Somatostatin: Likely the most widely effective gastrointestinal hormone in the human body

Table 2 The 5 subtypes of human SS receptors

Feature	SS receptors
	Subtype 1	Subtype 2	Subtype 3	Subtype 4	Subtype 5
Amino acid sequence	361	369 (A), 346 (B)	418	388	364
Chromosomal location	14	17	22 20	20 22	16
G protein coupling	Yes	Yes	Yes	Yes	Yes
Effector system
Adenylate cyclase activity	Reduced	Reduced	Reduced	Reduced	Reduced
Tyrosine phosphatase activity	Increased	Increased	Not investigated	Not investigated	Not investigated
Possible binding affinity to receptors
SS-14	++	++	++	++	++
SS-28	++	++	++	++	++
Octreotide	±	++	+	±	++
Vapreotide (RC-100)	±	++	+	+	+++
Lanreotide (BIM-23014)	±	++	+	+	+++
1Distribution in normal human tissue	Brain, lungs, stomach, jejunum, kidneys, liver, pancreas	Brain, kidneys	Brain, pancreas	Brain, lungs	Brain, heart, adrenal glands, placenta, pituitary, small intestine, skeletal muscle

¹Not all human tissues were tested simultaneously. This table was modified from Steven et al.